First i must apologize for the bad english coming up, Im not used to writing math in english.
If T1 is a regular triangle with its points A,B,C above the x axis and s0(T1) is the mirror image under the x-axis, with points A',B',C', what then is meant by the union T2 = T1 ∪ s0(T1)?
Since I am to discuss T2s isometrics, I figure it must be a polygon, but Im not sure which one.
Thanks!